Titanium nitride exhibits a wide variety of characteristics, including extreme hardness, abrasion resistance, high melting temperature, high corrosion resistance and electrical conductivity. Because of these various characteristics, titanium nitride films are extremely important in a wide range of applications. Titanium nitride films are used, for example, as wear-resistent coatings for cutting tools and other mechanical parts, and for high temperature structural materials. An increasingly important use of titanium nitride films is in the microelectronic industry. Titanium nitride films are especially useful as diffusion barriers in electronic devices, particularly against diffusion between aluminum and silicon, and as planarization and interconnect material, particularly in multi-level metallization schemes.
There are a wide variety of techniques for synthesizing titanium nitride films on different substrates. Prior techniques for synthesizing titanium nitride films include chemical vapor deposition and sputtering, such as that taught in H. Itoh et al., "Chemical Vapour Deposition of Corrosion-Resistant TiN Film to the Inner Walls of Long Steel Tubes," J.Mat.Sci., 21, 751-56 (1986) and D. S. Williams et al., "Nitrogen, Oxygen, and Argon Incorporation During Reactive Sputter Deposition of Titanium Nitride," J.Vac.Sci.Technol. B, 5, 1723-29 (1987). Another prior technique used to apply a titanium nitride film to the surface of a substrate is ion implantation, such as that taught in B. Rauschenbach, "Formation of Compounds by High-Flux Nitrogen Ion Implantation in Titanium," J.Mat.Sci., 21, 395-404 (1986), M. Belii et al., Formation of Chemical Compounds by Ion Bombardment of Thin Transition Metal Films," Phys.Status Solidi A, 45, 343-52 (1978), and P. A. Chen et al., "Titanium Nitride Films Prepared by Ion Implantation," Thin Solid Films, 82, L91-92 (1981).
Yet another technique is the pyrolysis of preceramic polymers. D. Seyferth et al., "Preparation of Titanium Nitride and Titanium Carbonitride by the Pre-ceramic Polymer Route," J.Mat.Sci.Lett., 7, 487-88 (1988)). Kamiya, et al., "Nitridation of the Sol-gel Derived Titanium Oxide Films by Heating in Ammonia Gas," J.Am.Cerm.Soc., 73, 2750-52 (1980), disclose the synthesis of titanium nitride films by slowly heating sol-gel derived titanium oxide films in ammonium gas.
These prior procedures, however, can have inherent limitations. For example, the surface size or shape of a substrate can limit the use of many of these known techniques, in particular chemical vapor deposition, sputtering, and ion implantation. These limitations limit the use of titanium nitride films particularly where planarization and/or the filling of vias in multilevel metallization is required. Significantly, these techniques can also result in titanium nitride films which contain high levels of impurities, such as oxygen, which in turn adversely affect the desired characteristics of the final product. For example, the level of oxygen in the nonstoichiometric films taught by Kamiya et al result in decreased conductivity and decreased barrier efficiency.